Many surfactants are phytotoxic. Non-ionic ethoxylates reduce growth and viability at lower concentrations than ionics, yet survival rates are higher at 1000 ppm levels of the former. The ionics cause severe ultrastructural change. Drastic changes in morphology, loss of membrane, swelling of thylakoids and appearance of dense osmophilic granules are evident in chloroplasts. Other effects include disintegration of polysomes into monosomes; swelling of mitochondria; dispersion of chromatin in the nucleus; appearance of unidentified vesicles in the cytoplasm and plasmolysis of cells. These effects can be attributed to possible emulsification of membrane lipids as well as precipitation and dispersion of cellular protein. No correlation seems to exist between biological effects and surface tension, but a coincidence may exist between interfacial tension reduction by ethoxylates and increased phytotoxicity. Correlations between biotoxicity of surfactants and factors such as molecular structure, hydrophilic-lipophilic balance, number of ethylene oxide units, acidic chain, molecular weight and branching are difficult, if not impossible to find because of scarcity of data. This project aims to investigate the factors which determine the biological effects of surfactants by employing a specially synthesized systematic series of compounds as well as several plants, tissue cultures, human cells and Hydra.